This invention relates to the discovery and asexual propagation of a new variety of grapevine, Vitis vinifera cv. xe2x80x98Sugratwentyonexe2x80x99. The new variety was first hybridized by David W. Cain in Wasco, Kern County, Calif., the variety being originated by controlled bybridization and subsequent ovule culture of normally abortive seeds. The new xe2x80x98Sugratwentyonexe2x80x99 variety is characterized by producing large clusters of red, naturally large seedless berries that are uniform, crisp and round.
The seed parent is xe2x80x98Sun World Breeding Selection 90089-165-268xe2x80x99 (nonpatented). The pollen parent is xe2x80x98Sun World International Breeding Selection 90227-127-008xe2x80x99 (nonpatented). The parent varieties were first crossed in May, 1993, with the date of first flowering being May, 1995. The new xe2x80x98Sugratwentyonexe2x80x99 variety was first asexually propagated by David W. Cain in December, 1995, near Wasco, Kern County, Calif., using hardwood cuttings.
The new grapevine variety cv. xe2x80x98Sugratwentyonexe2x80x99 differs from its seed parent by producing larger, more nearly round light red berries (as compared to the smaller, reddish-black berries of the seed parent) that ripen approximately one month later. xe2x80x98Sugratwentyonexe2x80x99 differs from its pollen parent by producing berries that are rounder and light red in color, in comparison to the oval, black berries of the pollen parent.
The new variety cv. xe2x80x98Sugratwentyonexe2x80x99 can be distinguished from commonly grown grape varieties such as the xe2x80x98Redglobexe2x80x99 (U.S. Plant Pat. No. 4,787) and the xe2x80x98Flame Seedlessxe2x80x99 (nonpatented) by possessing large clusters of red seedless berries that are crisp and uniform. The berries of the new xe2x80x98Sugratwentyonexe2x80x99 variety color with some difficulty in hot conditions, and are prone to bunch rot due to a combination of thin skin and a slightly compact cluster structure. Moreover, the berries of xe2x80x98Sugratwentyonexe2x80x99 are naturally very large, being among the largest of known seedless grapes. Manipulation by either gibberellic acid or girdling produces berries that are even larger. The berries are strongly attached to the cluster, mainly due to increased lignification of the peduncle, rachis, pedicel, and torus.
xe2x80x98Sugratwentyonexe2x80x99 most nearly resembles the xe2x80x98Redglobexe2x80x99 variety, but is distinguished from xe2x80x98Redglobexe2x80x99 by forming berries that are slightly smaller and contain small, vestigial seed remnants as compared to the xe2x80x98Redglobexe2x80x99 variety. The new variety cv. xe2x80x98Sugratwentyonexe2x80x99 remotely resembles the xe2x80x98Flame Seedlessxe2x80x99 variety, but produces berries that are naturally much larger, ripening about six weeks after the xe2x80x98Flame Seedlessxe2x80x99 variety.
The new xe2x80x98Sugratwentyonexe2x80x99 variety has been shown to maintain its distinguishing characteristics through successive asexual propagations by, for example, cuttings.